A technology (optical topography system) which measures variations in blood volume in a cerebral cortex with brain activity at multiple points and displays the variations in blood volume as a dynamic image or a static image has already been disclosed in Medical Physics, vol. 22, No. 12 pp. 1997-2005 (1995) (Atsushi Maki, Yuichi Yamashita, Yoshitoshi Ito, Eijyu Watanabe, Yoshiaki Mayanagi, and Hideki Koizumi, “Spatial and temporal analysis of human motor activity”), and in “Non-invasive measurement of language function by using optical topography”, Proceedings of SPIE, vol. 3597, pp. 230-237 (Tsuyoshi Yamamoto, Yuichi Yamashita, Hiroshi Yoshizawa, Atsushi Maki, Makoto Iwata, Eiju Watanabe, Hideaki Koizumi). In these papers, probes in an arrangement as shown in FIG. 1 are used. Eight irradiated points 1 to which optical fibers for incident lights are connected and eight light receiving points 2 to which optical fibers for detecting light are connected are alternately arranged on a shell 3 configured as a tetragonal lattice with 30-mm spacings. Substantially middle points between the irradiated points and the light receiving points are designated as sampling points 4. It follows therefore that the total of twenty-four sampling points are present with about 21-mm spacings over a region of 90 mm×90 mm. In the foregoing optical topography system, nearly uniform distances (which are 30 mm in FIG. 1) should be provided between the irradiated points and the light receiving points with the sampling points interposed therebetween.
Since it is difficult to bring a probe configured as a tetragonal lattice as described above into close contact with an entire spherical head, the following inventions have already been disclosed.
Probes for an optical topography system having branched portions extending from a coupling shaft to fit to the configuration of a head are disclosed in Japanese Laid-Open Patent Publication No. 2001-286449.
Probes for an optical topography system arranged in a lattice configuration which are characterized in that the coupler for the probes rotate and holders for holding the individual probes have elasticity are disclosed in Japanese Laid-Open Patent Publication No. 2002-143169.
Probes which cover an entire head by filling a plurality of regions of the head with tetragonal lattices and filling the gaps therebetween with polygons are disclosed in Japanese Laid-Open Patent Publication No. 2002-11012.
On the other hand, a system for non-invasively measuring the brain tissue of a subject by geometrically arranging probes on the head of the subject is disclosed in Domestic-Phase PCT Patent Application No. 2002-502653.
However, the optical topography systems and probes described above have the following problems.
Since the probes described above partially cover a head or cover the entire head by dividing the head into regions and placing a probe set on each of the regions, it has been impossible to represent the metabolic state of an entire brain as a single continuous image. In the conventional probe arrangement configured as a tetragonal lattice, it has been difficult to cover at least the upper half of a head by arranging a plurality of irradiated/light receiving point sets, while maintaining nearly uniform distances between the irradiated/light receiving points.